GI Physiology

Which of the following is not a stimulant for "CCK" release? a) amino acid b) monoglycerides c) small peptides d) fatty acids e) triglycerides

e) triglycerides

What are the three sublayers of the intestinal mucosa?

(inside to outside) *Epithelium (responsible for absorption of nutrients; contains glands) *Lamina propria (helps support the epithelium) *Muscularis mucosa

Gastric Motility

* * * * * *

Fill in the blanks

1. Lumen 2. Mucosa 3. Submucosa 4. Muscularis Propria 5. Glands 6. Lamina Propria 7. Muscularis mucosa

An investigator is studying epithelial repair in the small intestine of an experimental animal. The plain is to identify the location of the most active cell division. This cell activity is most likely to be found in which of the following regions? A) Base of the crypt B) Brunner glands C) Peyer patches D) Top of the villi

A) Base of the crypt

Which endogenous substances increase gastric acid secretion?

Acetylcholine (neurocrine) Gastrin (endocrine) Histamine (paracrine) Gastrin-releasing peptide (GRP), which acts to increase gastrin secretion

Valves of Kerckring are seen in the ______? A. Appendix B. Small Intestine C. Cecum D. Sigmoid Colon E. Rectum

B. Small Intestine

A healthy 24-year-old man is participating in a study of swallowing. The manometric pressure changes that occur while this man swallows are shown. Which of the following traces best represents muscle activity in the upper esophageal sphincter? A) B) C) D) E)?

D

Plicae Circularis/ Valves of Kerckring

Circular folds that involve *both mucosa and submucosa* *Increase the SA * * *located primarily in jejunum?

An investigator is studying obesity and appetite in an experimental mouse. The mouse is obese and markedly smaller than the rest of the mice in the same litter. The mouse is also found to be infertile. Further investigation of the mouse shows deficiency of a protein that regulates appetite. The protein is purified and administered by injection daily for 2 weeks. At the end of 2 weeks, the mouse is eating less food, has had a weight loss of 20% of its initial body weight, and has an increased basal metabolic rate. Which of the following proteins was most likely injected into this mouse? A) Cholecystokinin B) Ghrelin C) Glucagon-like peptide D) Insulin E) Leptin F) Neuropeptide Y

E) Leptin

Swallowing is a completely voluntary process T/F?

F! Swallowing is initiated voluntarily in the mouth, but thereafter it is under involuntary or reflex control

Which is the only gastrointestinal hormone that is secreted in response to all three types of nutrients?

Glucose-dependent insulinotropic peptide (GIP)

What are the two types of Small Intestinal Contractions? Describe Them

Segmentation Contraction and Peristaltic Contraction Segmentation * * * * * * * Peristaltic * * * * * *

Which endogenous substances reduce gastric acid secretion?

Somatostatin Secretin Gastric inhibitory peptide (GIP) Vasoactive intestinal peptide (VIP) Prostaglandins E and

In what histologic gut layer is Meissner's plexus located?

Submucosa

The submucosal plexus lies between the _________ and the _____________ The myenteric plexus lies between the _________ and the _____________

Submucosal (Meissner's): between the sumucosa and the circular muscle layer Myenteric (Auerbach's): between the circular muscle layer and longitudinal muscle layer

Why is chronic proton pump inhibitor (PPI) use associated with high levels of gastrin?

This is because the main stimulus to the suppression of gastrin release is acid If acid production is suppressed, gastrin levels go up

Describe the distribution of skeletal and smooth muscle on the upper, lower, and middle part of the esophagus.

Upper 1/3: Striated skeletal muscle Middle: Mix of skeletal and smooth Lower 1/3: Smooth muscle FIND A PIC

Why do some babies develop "newborn jaundice"?

bc udp glucuronyl transferase is synthesized slowly after birth

The Vagus nerve provides parasypathetic innervation to which part of gut?

pelvic nerve to other half?

During a study of gastric parietal cells, an investigator attempts to elicit maximum hydrochloric acid secretion from the stomach of an experimental animal. Which of the following combinations of substances is most likely to lead to this desired effect? Acetylcholine Gastrin Histamine Secretin (A) Increased increased increased increased (B) Increased increased increased decreased (C) Increased decreased decreased increased (D) Decreased increased increased increased (E) Decreased decreased increased increased (F) Decreased decreased decreased decreased (G) Decreased decreased decreased decreased

(B) Increased Ach increased Gastrin increased Histamine decreased Secretin

After an overnight fast, a 52-year-old man undergoes infusion of acid through a catheter into the upper duodenum. This most likely will increase pancreatic secretion mainly through the action of which of the following substances? (A) Cholecystokinin (B) Gastrin (C) Glucagon (D) Secretin (E) Vasoactive intestinal polypeptide

(D) Secretin

A 75-year-old male presented with a 6-month history of early satiety and with upper abdominal discomfort for many years. Physical examination revealed mild epigastric tenderness. Esophago-gastro-duodenoscopy showed a large, ulcerated mass in the upper stomach, which was found to be cancerous. Surgery resulting in the removal of the gastric fundus was performed. After successful surgery, the patient was advised to eat small portions and to drink small volumes because of which of the following? (A) almost complete absence of gastric motility (B) distorted emptying of liquids (C) inadequate mixing of large food boluses (D) lack of receptive relaxation in the stomach (E) weaker and slower propulsion of food toward the pylorus

(D) lack of receptive relaxation in the stomach The receptive relaxation reflex is a feature of the oral stomach, composed of the fundus and upper stomach body. Without food, the orad stomach shows low frequency, sustained contractions that are responsible for generating a basal pressure within the stomach. When food enters the stomach, a reflex is initiated, which allows gastric accommodation of large increases in volume with only small increases in intragastric pressure

Which of the following statements is TRUE regarding radiographic differences in appearance between the small and large bowels? (A)Transverse linear densities that arise from the bowel wall and extend part way into the lumen are characteristically seen in the small intestine (B)Haustrae are the transverse linear densities found in the small intestine (C)Transverse linear densities that extend completely across the bowel lumen are found in the colon (D)Plicae circulares are the transverse linear densities found in the colon (E)Haustrae are less numerous and situated farther apart than plicae circulares

(E)Haustrae are less numerous and situated farther apart than plicae circulares

Gastrocolic Reflex

* * * * * *

Rectosphincteric Reflex

* * * * * *

Receptive Relaxation

* * * * * vagovagal reflex that is triggered by VIP.

Migrating Myoelectric Complexes (MMC)

*A propulsive movement initiated during fasting *Begins in the stomach and moves undigested material from the stomach and small intestine into the colon. *Repeats every 90-120 minutes during fasting. *When one movement reaches the distal ileum, a new one starts in the stomach *Mediated by motilin* *Function to clear the stomach of any residue from the previous meal *This movement prevents the backflow of bacteria from the colon into the ileum and its subsequent overgrowth in the distal ileum. * * *

By which 2 mechanisms does gastrin induce gastric H+ secretion? Which mechanism predominates?

*Gastrin binds CCKB receptors on ECL cells, inducing histamine release. Histamine increases HCL secretion via parietal cells (Indirect) *Binding and activating the CCKB receptor of parietal cells, which increases intracellular IP3 and Ca2+ via the Gq pathway (Direct) Gastrin increases acid secretion primarily through its effects on ECL cells (leading to histamine release) rather than through its direct effect on parietal cells

Intraesophageal Pressure is less than, equal to, greater than *Intrathoracic Pressure *Atmospheric Pressure *Abdominal Pressure

*Intrathoracic Pressure: = *Atmospheric Pressure: < (UES keeps air out) *Abdominal Pressure < (LES keeps stomach contents out)

Leptin and Grehlin

*Leptin secreted by adipocytes *Grehlin secreted by P/D1 cells (stomach) *Both hormones act on receptors in the arcuate nucleus of the hypothalamus *Both hormones able to cross the BBB *

What are the four layers of the GI wall?

*MSMS* Mucosa (facing lumen) Submucosa Muscularis Propria/Externa Serosa/Adventitia (facing blood)

VIPoma

*Neoplasm that produces ectopic vasoactive intestinal peptide (VIP) *Arise from the pancreas in 90% of cases *5% are associated with MEN 1 **The dominant symptom is profuse diarrhea despite fasting* (leads to dehydration) *Also termed "WDHA syndrome" for Watery Diarrhea, Hypokalemia, Achlorhydria *Hypokalemia may present as muscle cramps or weakness *Metabolic Acidosis due to loss of bicarbonate in the diarrhea *Facial flushing is often present (due to peripheral vasodilatory effects of VIP) *Diarrhea is secretory and not osmotic *Tx: Octreotide (somatostain analogue) inhibits hormone release

Esophageal Phase of Swallowing

*Once food has passed through the UES, UES contracts *Primary peristaltic wave *If the Primary peristaltic wave is not successful, a secondary peristaltic wave is initiated by the local distention in the esophagus *Relaxation of LES via VIP and NO * * * * *Receptive Relaxation

Pharyngeal Phase of Swallowing

*Soft palate is pulled upward *adduction (bringing together or "approximation") of the true vocal folds to protect the tracheal *Epiglottis covers up the opening of the larynx *Upper Esophageal Sphincter relaxes to allow food to pass from pharynx into esophagus *A peristaltic wave of contraction begins in the pharynx that propels food through the UES

Each part of the GI tract has a characteristic Slow Wave frequency. Which part has the lowest frequency? Which part has the highest?

*Stomach = 3/ min (slowest) *Duodenum = 12/ min (fastest)

Oral Phase of Swallowing

*Tongue forces bolus back towards pharynx *Activation of somatosensory receptors in the pharynx *Sensory information is sent to the Swallowing center in the medulla => Initiates the Pharyngeal Phase

Somatostatinoma

*Tumor of the delta cells of the endocrine pancreas *Commonly found in head of pancreas *Associated with psamomma bodies *Symptoms -achlorhydria: blockage of gastin release -cholelithiasis: blockage of CCK release -steatorrhea: blockage of secretin release -diabetes mellitus/ hyperglycemia: blockage of *Tx: Somatostatin analogue (inhibit the secretion of somatostatin); Chemotherapy such as streptozocin; surgical resection

Slow Waves

*Unique feature of the electrical activity of GI smooth muscle *oscillating depolarization and repolarization of membrane potential of smooth muscle cells *action potentials occur "on top of" slow wave if membrane potential is depolarized to threshold *Slow waves themselves are not action potentials! *originate at interstitial cells of Cajal (ICC) * ICC = "pacemaker" for GI smooth muscle; located primarily in myenteric plexus *slow waves occur spontaneously in interstitial cells of Cajal driving the frequency of slow waves *Frequency of slow waves vary along GI tract; each part has a characteristic frequency *Stomach = 3/ min (slowest); Duodenum = 12/ min (fastest) *Freq. of Slow waves sets the Freq. of Action Potentials *Freq. of Action Potentials sets the strength of the contraction

Plicae Circularis vs Gastric Folds Plicae Circularis vs Colon Haustra

*Unlike gastric folds, they are permanent and not obliterated when the intestine is distended *The space between circular folds is smaller than the space between haustra of the colon (haustra are less numerous) *In contrast to haustra, circular folds reach around the whole circumference of the intestine

What are the main functions of Vasointestinal peptide?

*Vasodilation *Increases cAMP in intestinal epithelial cells;results in secretory diarrhea *Inhbition of gastric acid secretion *Stimulation of intestinal secretion *Smooth muscle cell relaxation (lower esophageal sphincter; sphincter of oddi) * Certain pathological conditions, such as achalasia and Hirschsprung disease, the lack of VIP innervation is believed to have a major role in defective esophageal relaxation and bowel dysmotility

Effect of Flow rate on Composition of Pancreatic Secretion

*When the pancreatic flow rate changes, the Na+ and K+ concentrations in pancreatic juice remain constant *Reciprocal relationship between Cl- and HCO3- concentrations *At highest flow rates high HCO3- and low Cl- at lowest flow rates low HCO3- and high Cl- **Regardless of flow rate, pancreatic secretion is always isotonic*

Gastric Emptying

*contractions periodically propel a portion of the gastric contents through the pyloric sphincter into the duodenum *gastric emptying is closely regulated to allow adequate time for neutralization of gastric acid in the duodenum *H+ receptors in the duodenum detect low pH (high H+) and act via interneurons in the myenteric (Auerbach's) nerve plexus to slow gastric emptying *Dec gastric emptying ensures gastric contents are delivered slowly to the duodenum allows adequate time for neutralization of gastric acid in the duodenum by pancreatic HCO3- *arrival of fatty acids in the duodenum stimulates cholecystokinin (CCK) secretion by I cells in the small intestine to slow gastric emptying *Dec gastric emptying ensures gastric contents are delivered slowly to the duodenum allows adequate time for fatty acid digestion and absorption in the small intestine

Mechanism of slow waves

*depolarization phase = inward Ca2+ current depolarizes cell membrane *repolarization phase = outward K+ current repolarizes cell membrane

The origin of electrical slow wave activity in gastrointestinal tract smooth muscle is A.The interstitial cells of Cajal B.The smooth muscle of the circular muscle layer C.The smooth muscle of the longitudinal muscle layer D.The smooth muscle of the muscularis mucosa E.The myenteric plexus

A)

The rate of gastric emptying increases with an increase in a. Intragastric volume b. Intraduodenal volume c. Fat content of duodenum d. Osmolality of duodenum e. Acidity of duodenum

A) The initial rate of emptying varies directly with the volume of the meal ingested. Gastric emptying is influenced by the intragastric volume and by the physical and chemical composition of the chyme in the small intestine. Increasing the volume, fat content, acidity, or osmolarity of the lumen of the small intestine elicits inhibitory neural (enterogastric reflex) and hormonal (enterogastrone) feedback mechanisms.

Which of the following hormones, produced by the dodenal and proximal jejunal mucosa, stimulates the release of pancreatic juice rich in digestive enzymes? A) Cholecystokinin B) Glucagon C) Pancreatic polypeptide D) Secretin E) Vasoactive intestinal polypeptide

A) Cholecystokinin CCK: increases pancreatic secretion of digestive enzymes Secretin: increases pancreatic secretion of HCO3 (bicarb)

A 67-year old woman with pernicious anemia has absent gastric parietal cells. An increase in which of the following is the most likely additional finding? A) Gastrin in blood B) Protein digestionin the stomach C) Secretin in blood D) Secretion of gastric acid E) Secretion of intrinsic factor

A) Gastrin in blood This is because the main stimulus to the suppression of gastrin release is acid In Pernicous anemia, parietal cells are absent and no longer able to produce HCl. If acid production is suppressed, gastrin levels go up

Release of which of the following peptides leads to an increase in the secretion of pancreatic enzymes into the small intestine? A. Cholecystokinin B. Gastrin C. Motilin D. Secretin E. Somatostatin

A. Cholecystokinin Release of cholecystokinin is stimulated by the presence of peptides, amino acids, or fatty acids in the small intestine. Cholecystokinin acts on the pancreas to stimulate secretion of pancreatic enzymes that aid in the digestion of these compounds. Secretin (choice D) secretion is stimulated by the presence of H+ and fatty acids in the duodenum, and causes an increase in pancreatic and biliary HCO3- release and a decrease in gastric H+ release.

A 42-year-old obese woman experiences episodic abdominal pain. She notes that the pain increases after the ingestion of a fatty meal. The action of which of the following hormones is responsible for the postprandial intensification of her symptoms? A. Cholecystokinin B. Gastrin C. Pepsin D. Secretin E. Somatostatin

A. Cholecystokinin The correct answer is A. This woman has a risk profile (female, fat, forties) and symptomatology consistent with gallstones (cholelithiasis). As would be expected, contraction of the gallbladder following a fatty meal often exacerbates the pain caused by gallstones. Cholecystokinin (CCK), the release of which is stimulated by dietary fat, is the hormone responsible for stimulation of gallbladder contraction. It is produced in I cells of the duodenum and jejunum. In addition to gallbladder contraction, CCK also stimulates pancreatic enzyme secretion and decreases the rate of gastric emptying.

Which of the following hormones is most important in initiating gall bladder contraction? A. Cholecystokinin (CCK) B. Gastric inhibitory peptide (GIP) C. Gastrin D. Secretin E. Vasoactive intestinal polypeptide (VIP)

A. Cholecystokinin (CCK) Cholecystokinin, or CCK, is synthesized in the duodenal and jejunal mucosa and stimulates gall bladder contraction and pancreatic enzyme secretion. Other functions include slowing of gastric emptying, an atrophic effect on the pancreas, and secretion of antral somatostatin, which in turn, decreases gastric acid secretion.

A patient with a history of gastroesophageal reflux disease has been taking proton pump inhibitors for the past 2 years. What effect will chronic proton pump inhibitor use have on serum gastrin levels? A. Serum gastrin levels will be increased B. Serum gastrin levels will be decreased C. Serum gastrin levels will be unchanged

A. Serum gastrin levels will be increased Proton pump inhibitors block the H+/K+ ATPase and cause an overall increase in stomach pH. Increased pH is a potent stimulus for the release of gastrin by antral G cells. As a result, serum gastrin levels will be elevated in a patient taking proton pump inhibitors.

The principal paracrine secretion involved in the inhibitory feedback regulation of gastric acid secretion is a. Gastrin b. Somatostatin c. Histamine d. Enterogastrone e. Acetylcholine

B)

Gastric emptying is regulated to ensure the chyme enters the duodenum at an appropriate rate. Which of the following factors promotes gastric emptying? A) Anorexia nervosa B) Antral peristalsis C) Bulimia nervosa D) Obesity E) Scleroderma F) Type I diabetes

B) Antral peristalsis pushes chyme toward the pylorus and thus promotes gastric emptying. Other factors that promote gastric emptying include (a) decreased compliance of the stomach, (b) relaxation of the pylorus, and (c) an absence of segmentation contractions in the small bowel. Gastric emptying is thought to be slow in eating disorders such as anorexia nervosa, bulimia nervosa, and obesity. Scleroderma is a systemic disease that affects many organ systems. The symptoms result from progressive tissue fibrosis and occlusion of the microvasculature by excessive production and deposition of types I and III collagens. Deposition of fibrous tissues in the pylorus reduces gastric emptying. Gastroparesis (paralysis of the stomach) occurs in about 20% of type I diabetics. The high blood glucose is thought to damage the vagus nerve and thereby reduce gastric emptying. **Summary: Gastric emptying is decreased in Anorexia nervosa, Bulemia nervosa, Obesity, Scleroderma, and Type 1 Diabetes

The hormone involved in the initiation of the migrating motor complex is a. Gastrin b. Motilin c. Secretin d. Cholecystokinin e. Enterogastrone

B) Motilin is released during the interdigestive period and is believed to be involved in the initiation of the migrating motor complex. The factors responsible for release are unknown. All other gastrointestinal hormones are released during the digestive period and coordinate motor and secretory activities.

The interstitial cells of Cajal: A. fire action potentials to initiate the electrical slow waves propagating along the GI tract. B. Are found between the longitudinal and circular smoth muscle layers. C. Hormonally regulate peristalsis.

B) These cells are primarily located in the myenteric plexus

Emptying gastric contents into the small intestine is strictly controlled. Which of the following is most accurately represents this concept? A. High caloric meals empty faster. B. Liquid and solid meals empty at the same rate. C. Higher acidity in the stomach results in a slower rate of emptying. D. Tonicity of the gastric solution doesn't affect the rate of emptying.

C)

Which statement about gastrin is incorrect? a)gastrin stimulates growth of mucosa of the stomach b)the most potent releasers of gastrin are phenylalanine and tryptophan c)atropine blocks vagus-mediated gastrin release d)stomach distention stimulates gastrin secretion

C) *********

A 38-year-old man comes to the physician 24 hours after vomiting coffee-ground-like material. He has a 6-month history of intermittent, dull epigastric pain that is temporarily relieved with the use of antacids. Physical examination shows mild epigastric tenderness. Upper gastrointestinal endoscopy shows a duodenal ulcer Serum studies show markedly increased circulating concentrations of gastrin. Gastrin mediated hyperstimulation of which of the following cell types has contributed the most to the development of a duodenal ulcer in this patient? A) Acinar cells of Brunner glands B) Centroacinar cells C) Enleroendocrine cells D) Gastric chief cells E) Mucous neck cells F} Paneth cells G) Parietal cells H) Surface mucous cells

C) Enleroendocrine cells The NBME answer key says G??? This contradicts FA however. Which do we go with??

A 45 year old woman comes to the physician because she recently was diagnosed with cholelithiasis. She asks the physician why her abdominal pain is intermittent and not constant. The physician explains that pain is produced when the gallbladder contracts against the gallstone that is obstructing the cystic duct. Secretion of hormones from which of the following cells is the most likely cause of this contraction? A) Centroacinar cells of the exocrine pancreas B) Chief cells of the gastric mucosa C) Enteroendocrine cells of the small intestine D) Gastric parietal cells E) Vasoactive intestinal polypeptide-producing cells of the jejunal mucosa

C) Enteroendocrine cells of the small intestine CCK is synthesized and released by enteroendocrine cells in the mucosal lining of the small intestine (mostly in the duodenum and jejunum), called I cells,

Which gastrointestinal motor activity is most affected by vagotomy? a. Secondary esophageal peristalsis b. Distention-induced intestinal segmentation c. Orad stomach accommodation d. Caudad stomach peristalsis e. Migrating motor complexes

C) Orad stomach accommodation

Which statement about gastrin is incorrect? A) gastrin stimulates growth of gastric mucosa of the small intestine and colon B) the most potent releasers of gastrin are phenylalanine and tryptophan C) atropine blocks vagus mediated gastrin release D) stomach distension stimulates gastrin secretion

C) atropine blocks vagus mediated gastrin release Atropine does not block vagus mediated gastrin release , since the mediator is GRP not Ach

A 42-year-old male develops watery diarrhea. He denies any fevers or unintended weight loss. His potassium is found to be 2.8 mEq/L. A stool sample is negative for ova and parasites. His diarrhea resolves with octreotide therapy. What is the most likely diagnosis? A. Enterotoxigenic E. Coli B. Clostridium difficile C. VIPoma D. Gastrinoma E. Colon adenocarcinoma

C. VIPoma Watery diarrhea with hypokalemia and achlorhydria is classic for a VIPoma. VIPomas are tumors that secrete vasoactive intestinal peptide (VIP) and in adults, the tumor is usually located in the pancreas. VIP causes relaxation of smooth muscle and an increase in gastrointestinal secretion as a result of cAMP production. In addition, VIP stimulates lipolysis and glycogenolysis. VIP also stimulates pancreatic bicarbonate secretion and inhibits gastric hydrochloric acid secretion. Octreotide, which is a somatostatin analogue, is effective in treating VIPomas. Glucocorticoids are also effective. The other choices are incorrect

Why does the sensation of fullness last longer after a fatty meal?

CCK is secreted primarily in response to fatty acids entering the duodenum. One of the effects of CCK is to delay gastric emptying

Compare the effects of Secretin and CCK on bile and pancreatic secretions

CCK: increases pancreatic secretion of digestive enzymes Secretin: increases pancreatic secretion of HCO3 (bicarb) CCK: increases bile release by the gall bladder (contraction of gall bladder and relaxation of sphincter of oddi) Secretin: increases bile production and secretion by the liver

The circular and longitudinal muscle of the GI tract have antagonistic actions. Describe their effects

Contraction of Circular: narrows and elongates the relevant portion Contraction of Longitudinal: shortens and dilates the relevant portion

A 60-year-old woman is admitted to the hospital with a fever and severe diarrhea for the last 24 hours. Cultures of blood, cerebrospinal fluid, urine, and stool are all negative for pathogens. The profile of gut hormones reveals elevated levels of VIP. An analogue of which of the following would most likely lower her VIP levels? A) Erythromycin B) Histamine C) Motilin D) Somatostatin E) Trypsin

D) Somatostatin Octreotide, which is a somatostatin analogue, is effective in treating VIPomas

Muscles in the propulsive and receiving segments of the GI tract respond differently to food movement through the gut. Which of the following statements correctly describes activity in the propulsive segment? A. The circular and longitudinal muscles are contracted. B. The longitudinal muscles are contracted and the circular muscles are relaxed. C. Both the longitudinal muscles and circular muscles are relaxed. D. The circular muscles are contracted and the longitudinal muscles are relaxed

D. The circular muscles are contracted and the longitudinal muscles are relaxed

A 49 year old man is brought to the emergency department 30 minutes after fainting in the street. He regained consciousness 1 minute after fainting. He says that he has had watery diarrhea during the past 5 days which has not improved with fasting. He has not changed his diet or traveled overseas recently. His blood pressure is 90/60 mm Hg. Physical examination shows a flushed face and dehydration. Serum studies show a potassium concentration of 2 mEq/L and glucose concentration of 150 mg/dL. He is admitted to the hospital and intravenous fluid replacement is started. Over the next day, he passes a stool with a volume of 3.5L. Which of the following is the most likely cause of this patient's diarrhea? A) Bacterial overgrowth B) Cholera C) Inactivation of lipase D) Lactose intolerance E) Vasoactive intestinal polypeptide secretion

E) Vipoma The dominant symptom is profuse diarrhea despite fasting

A 50 year old man is taking several medications that affect his autonomic nervous system. The autonomic system control gut motility by changing which of the followings? A-Gastrin secretion B-Pacemaker discharge frequency C-Secretin secretion D-Slow wave frequency E-Spike potential frequency

E-Spike potential frequency Although neural input and hormonal input do not influence the frequency of slow waves, they do influence the frequency of action potentials and the force of contraction Parasympathetic stimulation and the hormones gastrin and motilin increase the frequency of action potentials and the force of gastric contractions. Sympathetic stimulation and the hormones secretin and GIP decrease the frequency of action potentials and the force of contractions.

T/F? The longitudinal muscle layer is thick and is densely innervated, whereas the circular muscle layer is thin and contains few nerve fibers

F Longitudinal: Thin, few nerves Circular: Thick, densely innervated (Pencil dick vs Chode)

An IV glucose load is utilized by cells more rapidly than an equivalent oral glucose load. T/F?

F! Oral glucose stimulates incretin secretion (GLP-1 and GIP), which stimulates insulin secretion (in addition to the direct stimulatory action of absorbed glucose on the Beta cells). Glucose given intravenously stimulates insulin secretion only by the direct action on the Beta cells (No Incretin Effect)

What are incretins?

Gastrointestinal hormones that promote the secretion of insulin Ex: GLP-1 (from K Cells) and GIP (From L Cells) As well as stimulating insulin secretion by Beta Cells of the pancreas, both also inhibit gastric emptying GLP-1 has a half-life of less than 2 minutes, due to rapid degradation by the enzyme dipeptidyl peptidase-4

The thickness of the stomach muscle wall increases from ____________ (proximal/distal) to ____________ (proximal/distal)

Increases from proximal to distal

Which type of food empties faster from the stomach into the SI; Liquids or Solids? Isotonic or Hypotonic or Hypertonic?

Liquids > Solids Isotonic > Hypotonic/Hypertonic

Where is the Swallowing Center located in the brain?

Medulla Oblongota

What nerve plexus directly provides parasympathetic innervation to the gut epithelium and muscularis mucosa?

Meissner's plexus contains parasympathetic ganglia. It is the site of parasympathetic innervation of the gut epithelium and muscularis mucosa.

Compare the innervation, function, and location o the Myenteric and Submucosal Plexus

Myenteric (Auerbach's) -Muscularis externa -Controls motility -Receives input from both sympathetic and parasympathetic Submucosal (Meissner's) -Submucosa -Controls blood flow, secretions, and absorptions -*Receives input from only parasympathetic*

What are the two functional divisions of the stomach? Describe them

Orad Stomach and Caudad Stomach Orad: *Proximal *Contains Fundus and Proximal Body *Thin Walled *Function is to receive the bolus Caudad: *Distal *Contains Distal Body and Antrum *Thick Walled (stronger contractions) *Function is to mix and propel food into SI

What are the three phases of Swallowing? Which is voluntary?

Oral, Pharyngeal, and Esophageal Oral Phase = Voluntary

All of the contractile tissue of the GI tract is smooth muscle. Where are the exceptions?

Pharynx Upper 1/3 of Esophagus External Anal Sphincter (these are striated muscle)

Phasic vs Tonic Contractions of GI Smooth Muscle

Phasic *periodic contractions followed by relaxation *found in esophagus, gastric antrum, small intestine (All the tissues involved in mixing and propulsion) Tonic *maintain a constant level of contraction or tone without regular periods of relaxation *found in upper/orad region of stomach, lower esophageal, ileocecal, and internal anal sphincters

Which two amino acids are the most potent releasers of gastrin?

Phenylalanine and Tryptophan

The Primary Peristaltic Wave of the Esophagus is mediated by? The Secondary Peristaltic Wave of the Esophagus is mediated by?

Primary: Swallowing Reflex Secondary: ENS (Enteric Nervous System)

During peristalsis, on the proximal side of the bolus, the circular muscle ____________(contracts/relaxes) and the longitudinal muscle -___________(contracts/relaxes) On the distal side of the bolus, the circular muscle ____________(contracts/relaxes) and the longitudinal muscle -___________(contracts/relaxes)

Proximal side: Circular muscles are contracted and the longitudinal muscles are relaxed => constriction of the segment of GI behind the bolus Vice Versa

What two smooth muscle layers are contained within the muscularis propria of the intestines?

The inner circular muscular layer, and the outer longitudinal muscular layer. Inner (closer to lumen) = circular outer = longitudinal

What is the role of smooth muscle in the gut muscularis mucosa?

The muscularis mucosa is the deepest layer of the gut mucosa, containing smooth muscle that keeps the mucosal surface motile.

During a study of pancreatic function in a fasted experimental animal, with a chronic pancreatic fistula. The researcher administers a variety of substances intravenously to mimc postprandial levels. The volume and composition of pancreatic secretions are then measured. The result is: High in efflux from pancreatic fistula, Low in protein content. Which of the following substances was most likely administered to obtain the results shown? a) Acetylcholine b) Cholecystokinin c) Gastrin-releasing peptide d) Secretin e) Somatostatin f) Vasoactive intestional polypeptide

d) Secretin Studies have shown that CCK by itself does not elicit a significant volume response by the pancreas. The effect of CCK is potentiated by Secretin which results in large increases. Furthermore, secretin alone causes a steady increase in pancreatic juice but there is only a low level of protein secreiton. A second way to look at this problem, is that secretin is not responsible for pancreatic enzyme (protein) secretion and therefore the protein content would be low